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Boot Options in a Boot.ini File

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Important

This topic describes the boot options supported in Windows XP and Windows Server 2003. If you are changing boot options for Windows 8, Windows Server 2012, Windows 7, Windows Server 2008, or Windows Vista, see Boot Options in Windows Vista and Later.]

Boot.ini is a text file located at the root of the system partition, typically c:\Boot.ini. Boot.ini stores boot options for computers with BIOS firmware, traditionally, computers with IA-32-based and x64-based processors. On Windows Server 2003 and earlier versions of the Windows NT family of operating systems, when the computer starts, the Windows boot loader, called "ntldr", reads the Boot.ini file and displays the entries for each operating system in the boot menu. Then, ntldr loads the selected operating system in accordance with settings in the Boot.ini file.

By default, on NTFS drives, the system, hidden, archived, and read-only attributes are set to protect Boot.ini; however, members of the Administrators group can change these attributes. The file attributes do not affect the operation of the boot loader.

The following sections briefly describe Boot.ini and explain the aspects of boot options that are specific to computers with Personal Computer Advanced Technology (PC/AT)-type BIOS firmware.

This section includes:

This document describes aspects of Boot.ini that are of special interest to driver developers and testers. For a complete list of Boot.ini parameters, see Available Switch Options for the Windows XP and the Windows Server 2003 Boot.ini Files topic on the Microsoft Support website.

Mapping Boot.ini Options to BCDEdit Options and Elements

The following table provides a mapping from the boot options used in operating systems prior to Windows Vista (in Boot.ini), to the BCDEdit options and the BCD elements used in Windows. For information about the BCD boot elements with the context of WMI, see BCD WMI Provider Reference.

Boot.ini BCDEdit option BCD element type

/3GB

increaseuserva

BcdOSLoaderInteger_IncreaseUserVa

/BASEVIDEO

vga

BcdOSLoaderBoolean_UseVgaDriver

/BOOTLOG

bootlog

BcdOSLoaderBoolean_BootLogInitialization

/BREAK

halbreakpoint

BcdOSLoaderBoolean_DebuggerHalBreakpoint

/CRASHDEBUG

/dbgsettings /start

/DEBUG, BOOTDEBUG

/debug

/bootdebug

BcdLibraryBoolean_DebuggerEnabled

/DEBUG

/debug

BcdOSLoaderBoolean_KernelDebuggerEnabled

/DEBUG, /DEBUGPORT=

/dbgsettings

BcdLibraryInteger_DebuggerType

/DEBUGPORT=

/dbgsettings

BcdLibraryInteger_SerialDebuggerPort

BcdLibraryInteger_SerialDebuggerBaudRate

BcdLibraryInteger_1394DebuggerChannel

BcdLibraryString_UsbDebuggerTargetName

BcdLibraryInteger_DebuggerNetHostIP

BcdLibraryInteger_DebuggerNetPort

BcdLibraryBoolean_DebuggerNetDhcp

BcdLibraryString_DebuggerNetKey

/EXECUTE

nx

BcdOSLoaderInteger_NxPolicy

/FASTDETECT

/HAL=

hal

BcdOSLoaderString_HalPath

/KERNEL=

kernel

BcdOSLoaderString_KernelPath

/MAXMEM=

truncatememory

BcdLibraryInteger_TruncatePhysicalMemory

/NODEBUG

/debug

/NOEXECUTE

nx {

BcdOSLoaderInteger_NxPolicy

/NOGUIBOOT

quietboot

BcdOSLoaderBoolean_DisableBootDisplay

/NOLOWMEM

nolowmem

BcdOSLoaderBoolean_NoLowMemory

/NOPAE

pae

BcdOSLoaderInteger_PAEPolicy

/ONECPU

onecpu

BcdOSLoaderBoolean_UseBootProcessorOnly

/PAE

pae

BcdOSLoaderInteger_PAEPolicy

/PCILOCK

usefirmwarepcisettings

BcdOSLoaderInteger_UseFirmwarePciSettings

/REDIRECT

/ems

/emssettings [ BIOS ] |

[ EMSPORT:{port} | [EMSBAUDRATE: {baudrate}] ]

BcdOSLoaderBoolean_EmsEnabled

/SOS

sos